Gold nanorods (AuNRs), because of their strong absorption of near-infrared (NIR) light, are very suitable for in vivo photothermal therapy of cancer. However, appropriate surface modification must be performed on AuNRs before their in vivo application because of the high toxicity of their original stabilizer cetyltrimethylammonium bromide. Multidentate ligands have attracted a lot of attention for modification of inorganic nanoparticles (NPs) because of their high ligand affinity and multifunctionality, while the therapeutic effect of multidentate ligands modified NPs in vivo remains unexplored. Here, we modified AuNRs with a polythiol PEG-based copolymer. The multidentate PEG coated AuNRs (AuNR-PTPEGm950) showed good stabilities in high saline condition and wide pH range. And they had much stronger resistance to ligand competition of dithiothreitol (DTT) than AuNRs coated by monothiol-anchored PEG. The AuNR-PTPEGm950 had very low cytotoxicity and showed high efficacy for the ablation of cancer cells in vitro. Moreover, the AuNR-PTPEGm950 showed good stability in serum, and they had a long circulation time in blood that led to a high accumulation in tumors after intravenous injection. In vivo photothermal therapy showed that tumors were completely cured without reoccurrence by one-time irradiation of NIR laser after a single injection of these multidentate PEG modified AuNRs.Keywords: cancer NIR photothermal therapy; gold nanorods; multidentate polyethylene glycol; surface modification; tumor accumulation;